General Science Quiz: Gas Laws and the Kinetic Theory of Gases

Boyle's law, established in 1662, says that for a fixed mass of gas at constant temperature the product of pressure and volume stays constant, so doubling the pressure halves the volume.

By Charles's law the volume of a fixed mass of gas at constant pressure is proportional to its absolute temperature, so heating the air inside the envelope makes it expand; some of it escapes from the open mouth, the mass of air left inside falls, its density becomes lower than…

Extending the straight line of Charles's law backwards shows that the volume of an ideal gas would become zero at minus 273.15 degrees Celsius, and this point is taken as the zero of the kelvin or absolute scale, at which molecular motion carries its least possible energy.

In SI units the universal gas constant is 8.314 joule per mole per kelvin, obtained by multiplying the Boltzmann constant by the Avogadro number.

Substituting one mole, 273.15 kelvin and one atmosphere in the ideal gas equation gives a volume of 22.4 litres, the molar volume at standard temperature and pressure, and this is the figure used in mole calculations; with the modern standard pressure of one bar the value works out to about…

Graham's law of diffusion states that at the same temperature and pressure the rate at which a gas diffuses is inversely proportional to the square root of its density, and therefore of its molar mass.

The kinetic theory gives the average kinetic energy of a molecule as three halves of the product of the Boltzmann constant and the absolute temperature, and for one mole as three halves of RT.

Temperature is a measure of the average kinetic energy of the particles of a substance, in a solid as in a gas: in a solid the particles are held in fixed positions but vibrate about them, and heating makes the vibrations faster and wider, so the average kinetic energy rises…

The kinetic theory of an ideal gas assumes exactly the opposite: that there are no forces of attraction or repulsion between molecules except during the brief moment of a collision.

The root mean square speed follows from the kinetic gas equation and equals the square root of three RT divided by the molar mass, or equally the square root of three times the Boltzmann constant times the temperature divided by the mass of one molecule.

The law states that for a mixture of gases that do not react, the total pressure is the sum of the partial pressures each gas would exert if it alone occupied the whole volume at the same temperature.